Objective: Laboratory studies with animals and cells in culture have shown cancer preventive activity of polyphenols isolated from red wine and green tea. However, the basic molecular mechanisms by which these polyphenols inhibit carcinogenesis have not been completely elucidated. The objective of this study is to use two of these polyphenols (resveratrol and epigallocatechin gallate (EGCG) (and investigate their effects on the cell cycle control of G1-to-S phase transition, a critical molecular event in the carcinogenic process. Two series of cells in culture will be used for this study: (1) JB6 mouse epidermal cells and (2) mammary epithelial cells.